Oil compensator for mold strippers



July 5, 1932- EGGERT OIL CQMPENSATOR FOR MOLD STRIPPERS Filed Aug. so, 1929 3 U ,w gw J JMW I n M 5 6 in VT# 7 5 Patented July 5, 1932 PATENT OFFICE LEWIS EGGERTQOF TOLEDO, OHIO OIL COIMVPENSATOR FOR MOLD STRIPIPERS Application iled August 30, 1929. Serial No. 389,394.

My invention relates to improvements in hydraulically operated molding machines.

One of the objects of my invention' is to automatically maintain the proper quantity of operating liuid in the system.

A further object is to entirely eliminate waste or loss of operating fluid from the system.

Other objects will appear hereinafter.

Referring to the drawing Fig. 1 is a view, partly in section, of a molding machine and the `various parts associated therewith in which my invention is embodied; and

i Fig. 2 is a top plan view of the control valve with its cover removed to Vshow the interior thereof.

The molding machine A shown in the drawing is known as a jolting or jarringmechanism. This machine has a table 1 at its upper end upon which the liask2 of the mold is placed.V The table 1V is intermittently jolted or vibrated up and down rapidly by air pressure, and the purpose of this operation is to jolt or ram the molding sand firmly and compactly about the pattern within the flask.

The pattern is mounted on a mold board or pattern plate 3 which is placed on .the table 1. The flask 2, which encloses the pattern and within which the molding 'sand is contained,

is placed on the pattern plate 3 and is firmly clamped against this pattern plate by means of pneumatically operated clamps 4;; y

The clamps are mounted at opposite points on the edge of the pattern plate and have clamping arms 5 which extend laterally to engage the upper edge of the flask and firmly clamp the flask against the pattern plate.

The clamping arms l1 are movable vertically either up or down to release or clampthe flask as the case may be and these arms are swung or rotated horizontally into and out of position relatively to the flask accordingly as the clamps 4 move upwardly to release the flask or downwardly to engage land clamp the flask, as set forth in my copending application Serial No. 389,393 of even date herewith. The clamps are connected by means of the pipes 6 and 7 to a suitable source of compressed airrepresented by the pipe 8.

Air Vpressure for the clamps is controlled by a slidevalve B. The chest 9 ofthis valve is connected directly ltothe source 8 of air supply. A sliding valve member 10 is contained within the chest and is intended to '.55 slide relatively to the ports 11 and 12 in the bottom wall of the chest for controlling the air for operating the clamps. The pipe 6 leading to the clamps is connected to the port 11 and the pipe 7 isconnected to the port 12. An exhaust port 13 is provided to which either of the other ports is connected throughjth'e chamber 14 of the slide valve member 10. These ports are so arrangedthat when the valve is in the position shown in Fig. 1 air pressure is admitted to the port 11 from the valve chest, and the port 12 is connected to the exhaust port 13. This admits air'pressure to operate the clamps downwardly for clamping operation. When the slide valve is at the opposite end of the chest the port 11 is connected to the exhaust port 13 and the port 12 will be uncovered by the valve member to admit pressure to the pipe 7 to operate the clamps upwardly for releasing the clamps. The slide valve is controlled by a motor ,driven mechanism 15, the operation of which is controlled in accordance with the system of control constituting they subject matter of my copending application Serial No. 389,392 of even date herewith.r

Associated with the jolting mechanism is a pair of strippers C which are positioned beneath the jolting' mechanism table1." These strippers have stripper pins or .rods 16 which extend vertically through the table 1 and pattern plate 3 to engage theunder edge of the flask. The pins are operated vertically bv the strippers to raise and lower the flask with respect to thejolting mechanism table. When 9@ a mold is completed the strippers are operated to elevate the mold, as indicated in dotted lines in Fig. 1, for stripping orseparating the mold from the pattern.k Any suitable handling machinery is then used to remove the completed mold and place an empty flask on the stripper pins for the next mold. The strippers are then lowered to place the flask on thev pattern plate and are allowed to remain'idle while the jolting mechanism op- 10C erates and until they are again required to raise the completed mold from the table. The clamps, of course, are arranged to operate in proper timed relation to the strippers so that after the strippers lower the flask on to the pattern plate the clamps will swing into clamping engagement with the flask. The clamps release and swing out of engagement to the lask just prior to the upward operation of the strippers.

The stripperscomprise stationary cylinders 17 in which plungers or pistons 1S are vertically reciprocable. The plungers have a cylindrical or cup-shaped casing 19 which extends downwardly outside of the stripper cylinder 17 to protect the mechanism from sand and dirt. The stripper pins at their lower ends are secured to ears 20 on these casings. The stripper plungers 18 contain oil or other suitable fluid 21 for hydraulically "operating the plungers. The lower ends of the plungers have ports 22 which communicate withV the cylinder chambers below the ends of the plungers. The upper ends of the plungers have ports 23 which are connected by the pipes 24 to the pipe 25 leading/to a suitable source of pressure. When pressure is applied to the oil in the plungers the oil. is forced downwardly through the ports 22 in the cylinder chamber and this forces the plunger upwardly. When the strippers are to be lowered the pressure is released, and the weight of the mold flask on the stripper per; force the plungers downwardly and force the oil from the cylinder chambers back through the ports 22 into the hollow plungers.

Pressure is applied to the oil by means of compressed air from the source 8 and controlled by the slide valve B. The pipe 25 is connected to a port 26 in the slide valve B in such manner that when the slide valve member is in the position shown in Fig. 1, the port is uncovered and pressure is admit-ted to the strippers. When the slide valve member is at the other end of its stroke it cuts ofi' pressure to the pipe line 25 but instead connects the port 26 to the exhaust port l13, thus releasing the pressure and allowing the strippers to lower, as hereinbefore explained.

It has been the practice in the past to exhaust the strippers directly into the atmosphere, hence whatever air had accumulated in the lines and strippers from the Vprevious operation would be exhausted directly into i the atmosphere by the lowering of the strippers. This gave rise to. operating dilficulties due to the fact 'that the exhaust air will carry more or less oil, and after each operation a small quantity of oil will becarried out of the system. It is necessary to maintain the proper amount of oil in the strippers but under these conditions it was quite difficult to do so. Furthermore as the quantity of oil in the stripper cylinders lowered air pockets were formed above the oil in the plungersV with the result that when the remaining quantity of oil in the plungers had been forced through the ports 17 into the cylinder chambers the air would follow the oil and continue to force the plungers upwardly but the air would have the effect of violently moving the stripper plungers at the upper portions of their stroke and the strippers would reach the upper limits of their stroke with a jerk. It is very necessary that the strippers operate very smoothly and steadily and not with a jerky movement especially at the upper ends of their stroke. If the movement is jerky or violent it will ar the sand loose from the mold and damage the mold.

I overcome these difficulties by preventing the exhaust waste of oil and by automatically maintaining the strippers full of oil at all times. Instead of connecting the exhaust port to the atmosphere I connect this port by means of the pipe 27 to an oil separator and accumulator l29. This is in the form of a tank to the upper end of which the pipe line 2S connects so that the exhaust oil drops to the bottom and accumulates in this tank. The air, free from oil, exhausts to the atmosphere through a port 30 near the upper end of the tank. The lower end of this tank is connected by the pipe 31 to the pipe 25 leading to the stripper cylinders. The tank is positionedconsiderably above the strippers and the pipe 31 sufliciently pitched so that when the strippers are idle while the jolting mechanism is operating, the accumulated oil in the tank will drain through the pipes 31 and 25 to the strippers and ,maintain the proper amount of oil in the strippers. The oil flows through the pipe 31 in the direction of the arrow during these replenishing or compensating periods. However, in order to prevent the reverse flow of oil or air through the pipe 31 whenl operating pressure is applied through the pipe 25, I provide a check valve 32 which automatically closes the pipe 31 against reverse flow of oil or air therethrough. This check valve may be of any suitable type for the purpose. The pipe 31 also has a hand operated valve 33 of any suitable construction which is normally left open but which may be closed if desired to cut off the tank from the line for repairs or other purpose.

Thus it will be seen that waste of oil from the systemis entirely eliminated, and the necessary quantity of oil for the proper operation of the strippers is constantly and automatically maintained. Any danger of jerking or violent operation of the strippers is thus entirely eliminated.

I am awarev that changes in the construction and arrangement of parts may be made without departing from the scope and spirit of the invention and I reserve the right to make such changes as fairly fall within the scopeof the appended claims.

I claim:

l. The combination of a fluid operated mechanism, means for applying air pressure to a liquid in said mechanism, means controlling the application of said air pressure onr the mechanism is idle, and a check valve for` preventing application of said air pressure in said accumulating means.

2. The combination of a fluid pressure operated mechanism containing a quantity of oil for operating said mechanism, means for supplying air pressure to said oil, means for releasing the air pressure and exhausting the air from said mechanism, means for separating oil from the exhaust air, means for returning the oil to the mechanism, and a check valve in said returning means for preventing back pressure in said separating means.

3. In a molding machine which has hydraulic operated strippers associated therewith containing a quantity of oil for operating the same, the combination of a pipe connecting said strippers with a source of air pressure, means for cutting ol the air pressure and exhausting the air pressure from said pipe, means for collecting the oil from the exhaust air, means for returning the collected oil to the pipe whereby the collected oil may flow therethrough when the air pressure is cut o", and means in the return means for preventing back pressure in the collecting means.

4. In a molding machine which has a hydraulically operated stripper associated therewith comprising a cylinder and a plunger movable therein, and means for admitting oil to said cylinder to operate the plunger, the combination of means for applying air pressure to the oil and including a pipe line, means for cutting off the air pressure and exhausting the pressure from the cylinder, a tank for collecting oil from the exhaust, means connecting the tank with the pipe line to return the collected oil to the cylinder while the air pressure is cut off, and means in the connecting means for prevent ing back pressure in the tank.

5. In a molding machine which has a hy- Y draulic stripper associated therewith comprising a cylinder and a piston operable therein, means for admittingoil to the cylinder for operating the piston, and a pipe line connected to the cylinder, the combination of a valve connecting said pipe to a source of air pressure, means operated by said valve for cutting off air pressure to said pipe and connecting the pipe to an exhaust outlet, a tank positioned above the strippers and connected to said exhaust for collecting the oil which is carried with the air from said outlet, a pipe connecting the tank with the first mentioned pipe to return the collected oil to said rst mentioned pipe when the pressure is cut 0H, and means in the pipe connecting the tank with the first pipe for preventing back pressure in the tank.

6; In a molding machine which has a hydraulic stripper associated therewith comprising a cylinder and a piston operable therein, means for admitting oil to the cylinder for operating the piston, and a pipe line connected to the cylinder, the combination of a valve connecting said pipe to a source of air pressure, means operated by said valve for cutting off air pressure to said pipe and connecting the pipe to an exhaust outlet, a tank positioned above the strippers and connected to said exhaust for collecting the oil which is carried with the air from said outlet, a pipe connecting the tank with the first mentioned pipe to return the collected oil to said first mentioned pipe, and a check valve in said second mentioned pipe for preventing the reverse flow of oil therein when pressure is applied to the lirst mentioned pipe.

LEWIS EGGERT. 

